Discussion of potential savings in fuel consumption of motor vehicles frequently mentions the automatic start/stop system. In this system, the internal combustion engine of the vehicle is automatically switched off during longer-lasting idling periods. If the user wishes to continue driving, he merely presses the accelerator pedal and the engine restarts automatically.
In a procedure of this type, referred to as a warm start, the electric starter motor of the internal combustion engine, referred to as the starter for short, must be driven with a very high power. If only a single battery, e.g. a lead-acid battery or lithium ion battery, is installed in a vehicle, a voltage dip occurs on the battery poles due to the high power requirement. As a result of this voltage dip, auxiliary equipment may not be supplied with sufficient power and may malfunction.
In the warm start, the starter is activated with a stationary armature. Since the starter is normally a series motor, a short circuit occurs via the armature winding. This results in a very high starting current, which may amount to several 100 A. However, the battery voltage on the battery poles normally dips at this time. This is also described, for example, in DIN 40839, which shows the voltage characteristic of the on-board supply voltage in a start-up curve.
In order to prevent malfunctions in the auxiliary equipment, such as, for example, navigation systems, car radios, telecommunication systems, air conditioning systems and the like, it is already proposed in the prior art to limit the starting current for a warm start. In particular, it is already proposed to operate the auxiliary equipment via a so-called back-up battery. This technology is known, for example, from DE 10 2007 062 955 A1. However, it is necessary here to trigger both the back-up battery and the main battery. Furthermore, the back-up battery increases the weight of the vehicle as a whole.
For this reason, the subject-matter was based on the object of providing a starting current limitation which provides maximum convenience with little structural outlay.